This invention relates to a process and apparatus for manufacturing a particle stabilized foamed metal, particularly a continuously produced slab of particle stabilized foamed aluminum.
Lightweight foamed metals have high strength-to-weight ratios and are extremely useful as load-bearing materials and as thermal insulators. Metallic foams are characterized by high impact energy absorption capacity, low thermal conductivity, good electrical conductivity and high absorptive acoustic properties.
A particle stabilized foamed metal of exceptional stability is described in Jin et al U.S. Pat. No. 4,973,358, issued Nov. 27, 1990. According to that patent, a composite of a metal matrix and finely divided solid stabilizer particles is heated above the liquidus temperature of the metal matrix. Gas is then introduced into the molten metal composite below the surface of the composite to form bubbles therein. These bubbles float to the top surface of the composite to produce on the surface a closed cell foam. This foamed melt is then cooled below the liquidus temperature of the melt to form a foamed metal product having a plurality of closed cells and the stabilizer particles dispersed within the metal matrix.
The foam which forms on the surface of the molten metal composite is a highly stable liquid foam.